Why the biological clock?
University of Pennsylvania biologists studying human reproduction have identified what is likely the major contributing factor to the maternal age-associated increase in aneuploidy, the term for an abnormal number of chromosomes during reproductive cell division. Using naturally aging mouse models, researchers showed that this basic fact of reproductive life is most likely caused by weakened chromosome cohesion. Older oocytes, or egg cells, have dramatically reduced amounts of a protein, REC8, that is essential for chromosomes to segregate correctly during the process that forms an egg. Mistakes in this process can create chromosomal abnormalities like Down syndrome. Richard Schultz, associate dean for the natural sciences and the Charles and William L. Day Distinguished Professor of Biology in Penn’s School of Arts and Sciences, and Michael Lampson, assistant professor of biology, found that kinetochores — the protein structures that mark the site where a chromosome pair is split duri
